[Courgette] Using LabelManager to reduce Courgette-apply peak RAM by 25%.

courgette/label_manager.h

Index: courgette/label_manager.h
diff --git a/courgette/label_manager.h b/courgette/label_manager.h
index d60a2746da22b6143476c387b5a5bf22e49682f0..4b2524053280ce0c4c377a4da10d87ab177dad02 100644
--- a/courgette/label_manager.h
+++ b/courgette/label_manager.h
@@ -80,10 +80,6 @@ class LabelManager {
   LabelManager();
   ~LabelManager();
 
-  // Returns an exclusive upper bound for all existing indexes in |labels_map|.
-  // TODO(huangs): Remove once all callers are gone.
-  static int GetIndexBound(const RVAToLabel& labels_map);
-
   // Returns an exclusive upper bound for all assigned indexes in |labels|.
   static int GetLabelIndexBound(const LabelVector& labels);